The enthalpy of formation of ethane at 25° C , if the enthalpies of combustion of carbon, hydrogen and ethane are 94.14,68.47 and 373.3 kcal respectively is

Question

The enthalpy of formation of ethane at 25° C , if the enthalpies of combustion of carbon, hydrogen and ethane are 94.14,68.47 and 373.3 kcal respectively is (A) 20.39 kcal (B) 210.69 kcal (C) -210.69 kcal (D) -20.39 kcal

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/chemistry/e6c80cd68d136958ddde3111927250b5-.png" /> (Heat of combustion is always negative.) The reaction shows the formation of ethane from its elemental constituent. Δ H text reaction =2(-94.14)+3(-68.47)-(-373.3)=-20.39 kcal

Q. The enthalpy of formation of ethane at $2 5^{\circ} C,$ if the enthalpies of combustion of carbon, hydrogen and ethane are $94.14, 68.47$ and $373.3 k c a l$ respectively is

$20.39 k c a l$

$210.69 k c a l$

$- 210.69 k c a l$

$- 20.39 k c a l$

(Heat of combustion is always negative.)

The reaction shows the formation of ethane from its elemental constituent.

$Δ H_{reaction} = 2 (- 94.14) + 3 (- 68.47) - (- 373.3) = - 20.39 k c a l$

Q. The enthalpy of formation of ethane at 25∘C, if the enthalpies of combustion of carbon, hydrogen and ethane are 94.14,68.47 and 373.3kcal respectively is

20.39kcal

210.69kcal

−210.69kcal

−20.39kcal